Question

I would like to redirect users to a custom page if their session has expired.

On PageLoad
If Session("OrgID") = Nothing Then
    Response.Redirect("SchoolLogin.aspx?schoolID="+[schoolid])
End If

I can store the schoolID in a hidden field on every page, but this doesn’t seem very elegant. I thought to try using the hidden field in a user control that I do have on every page, but the user control PageLoad fires after the main PageLoad so I’d get an error prior to checking for session expiration. Is there a common solution for this?

Answer 1

You can use QueryString, ViewState (ASP.NET’S built in hidden field) or setting it as a cookie value.

I don’t know enough about your scenario. The best I can offer is an example of how I deal with (what I am guessing) is similar to your situation.

Create a base class for all your page classes to inherit from (more here oldy but goody https://web.archive.org/web/20211020133935/https://www.4guysfromrolla.com/articles/041305-1.aspx), Add your SchoolId property to it. This is in c# I appologise, unfortunately VB.NET syntax literally makes my teeth jangle. It shouldn’t be too hard to translate though as this is pretty basic stuff.

Using QuertString, you would need to test for -1 and redirect in that case.

public class BasePage : System.Web.UI.Page
{
    public int SchoolId
    {
        get
        {
            if (Request.QueryString["schoolId"] != null)
            {
                return Convert.ToInt32(Request.QueryString["schoolId"]);
            }
            else
            {
                return -1;
            }
        }
    }
}

Using ViewState

public class BasePage : System.Web.UI.Page
{
    public int SchoolId
    {
        get
        {
            if (ViewState["schoolId"] != null)
            {
                return (int)ViewState["schoolId"];
            }
            else
            {
                int schoolId = someDataLayer.SelectUsersSchoolId(User.Identity.Name);
                ViewState["schoolId"] = schoolId;
                return schoolId;
            }
        }
    }
}

Using cookies (More here) http://msdn.microsoft.com/en-us/library/aa289495(v=vs.71).aspx

public class BasePage : System.Web.UI.Page
{
    public int SchoolId
    {
        get
        {
            if (Request.Cookies["schoolId"] != null)
            {
                return (int)Request.Cookies["schoolId"].Value;
            }
            else
            {
                int schoolId = someDataLayer.SelectUsersSchoolId(User.Identity.Name);
                Request.Cookies["schoolId"].Value = schoolId;
                Request.Cookies["schoolId"].Expires = DateTime.Now.AddDays(1);
                return schoolId;
            }
        }
    }
}